Dr. Gildow taught Microbe-Plant Interactions: Plant Disease and Biological Control (PPATH 405) an undergraduate senior level and introductory graduate level course.This course surveys biological interactions of plants with microbial organisms and viruses that are associated with causes of plant disease or that are involved in maintaining plant health (biological controls). The goal of the course is to educate students with the fundamental knowledge needed to apply basic plant pathology concepts for designing plant disease management strategies. Dr. Gildow was also adviser to the undergraduate Minor in Plant Pathology program.

Research Program:

Dr. Gildow's research was focused on three areas: (1) virus-cell membrane interactions associated with virus transport through insect vectors that determine vector-specificity; and (2) virus microevolution associated with infection of new plant host species and adaptation to new aphid vector species; (3) Studies of vector efficiency of aphids transmitting viruses of epidemiological importance;

Luteovirus vector-specificity mechanisms: Plant viruses in the family Luteoviridae, such as barley yellow dwarf virus (BYDV), potato leaf roll virus (PLRV), and soybean dwarf virus (SbDV), cause important diseases in major crops worldwide. Luteoviruses are small icosahedral ss-RNA viruses characterized by extreme host plant tissue-specificity infecting only phloem cells of plants within a limited host range and by vector-specificity limiting transmission by only one or a few aphid species. This extreme specificity for host tissue and vectors makes the luteoviruses excellent models for experimental studies of mechanisms regulating infection, cellular transport, virus transmission, and viral evolution associated with adaptations to new hosts and vectors. Much of his work has been on ultrastructural studies to identify the cellular mechanisms regulating luteovirus transport through aphid cell systems and identifying barriers to transmission that determine vector-specificity. Recent work in collaborations with Dr. Stewart Gray (USDA-ARS) at Cornell University is focused on identifying virus and aphid proteins associated with host tissue specificity and vector specificity.

Microevolution of Soybean Dwarf Virus and host/vector selection: Soybean dwarf luteovirus is an important pathogen on soybeans throughout Asia. In N. America, related SbDV strains occur commonly in perennial clovers but do not generally infect soybean at epidemic levels. Why clover isolates of SbDV do not infect soybeans has been unknown, but is believed to be due to the fact that until recently no N. American species of potential aphid vectors colonized soybean. In 2000, the soybean aphid (Aphis glycines) was introduced to N. America and soon thereafter, clover strains of SbDV were identified infecting soybean crops in several states. We have initiated studies to determine the likelihood of clover SbDV adapting to transmission by the soybean aphid and becoming epidemic in soybean crops. In general we are interested in how a virus responds when first introduced to a new host plant and adapts to that plant species, and how virus mutations may be selected for during adaptation to new aphid vector species. These studies are being done in collaboration with Dr. Bill Schneider and Dr. Vern Damsteegt (USDA-ARS; Ft Detrick, MD).

Identification of economically important aphid vectors : Recent virus transmission studies have centered on identifying the aphid species responsible for spreading plant viruses causing economically important crop diseases. Plum pox virus (PPV) in the virus family Potyviridae is a serious pathogen infecting stone fruits, like peaches, resulting in greatly reduced yields and killed trees. PPV was first identified in North America in Adams County, Pennsylvania in September, 1999. Surveys conducted in 2000 delineated the geographical range of the virus. My lab, with support from the Pa Dept. of Agr and the USDA-ARS, was responsible for identifying indigenous aphid species capable of transmitting the virus and determining which species were epidemiologically significant for spreading the virus. We were also involved in studies with Bill Schneider and colleagues (USDA-ARS, Foreign Disease and Weed Research Unit, Ft. Detrick, MD) to identify the host range of PPV in native and ornamental plant species that could function as reservoir hosts aiding PPV survival, and verified that infected fruits could play a role in spreading disease. Since 2010, PPV has been considered eradicated from Pennsylvania. More recently, strains of CMV capable of infecting legumes have become epidemic in many eastern US states. Significant yield losses have been reported in CMV-infected snap bean crops. Our research, supported by the PA Department of Agriculture in collaboration with Dr. Shelby Fleischer (Dept. Entomology) and colleagues at Cornell University, verified the major aphid vectors responsible for spreading CMV in snap bean fields. As part of this study we also developed experimental models for estimating vector efficiency in order to identify the most significant vectors responsible for CMV spread and allowing for more targeted control strategies.